DetectorClocksStandardTriggerLoader.h

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#ifndef LARDATAALG_DETECTORINFO_DETECTORCLOCKSSTANDARDTRIGGERLOADER_H
#define LARDATAALG_DETECTORINFO_DETECTORCLOCKSSTANDARDTRIGGERLOADER_H

// LArSoft libraries
#include "lardataobj/RawData/TriggerData.h" // raw::Trigger

// framework libraries
#include "canvas/Utilities/InputTag.h"
#include "cetlib_except/exception.h"

// C++ standard libraries
#include <optional>
#include <vector>

namespace detinfo {

  template <typename Event>
  std::optional<std::pair<double, double>> trigger_times_for_event(art::InputTag const& triggerTag,
                                                                   Event const& event)
  {
    // try to read the trigger from the event
    // fetch the trigger data product
    using TriggerHandle_t = typename Event::template HandleT<std::vector<raw::Trigger>>;

    TriggerHandle_t triggerHandle;
    if (!event.template getByLabel(triggerTag, triggerHandle)) { return std::nullopt; }

    // check that we do have a trigger
    // (we have already checked whether the handle is valid above)
    auto const& triggers = *triggerHandle;
    if (triggers.empty()) { return std::nullopt; }

    // select which trigger to set (i.e., the only one!)
    if (triggers.size() != 1) {
      throw cet::exception("setDetectorClocksStandardTrigger")
        << "Found " << triggers.size() << " trigger objects in '" << triggerTag.encode()
        << "' (only one trigger per event is supported)\n";
    }

    auto const& trigger = triggers.front();
    return std::make_optional(std::make_pair(trigger.TriggerTime(), trigger.BeamGateTime()));
  }

  template <typename Event>
  std::optional<double> g4ref_time_for_event(art::InputTag const& triggerTag, Event const& event)
  {
    // fetch the trigger data product
    using TriggerHandle_t = typename Event::template HandleT<std::vector<raw::Trigger>>;

    TriggerHandle_t triggerHandle;
    if (!event.template getByLabel(triggerTag, triggerHandle)) return std::nullopt;

    // check that we do have a trigger
    // (we have already checked whether the handle is valid above)
    auto const& triggers = *triggerHandle;
    if (triggers.empty()) return std::nullopt;

    // select which trigger to set (i.e., the only one!)
    if (triggers.size() != 1) {
      throw cet::exception("setDetectorClocksStandardTrigger")
        << "Found " << triggers.size() << " trigger objects in '" << triggerTag.encode()
        << "' (only one trigger per event is supported)\n";
    }

    return std::make_optional(triggers.front().TriggerTime());
  }

} // namespace detinfo

#endif // LARDATAALG_DETECTORINFO_DETECTORCLOCKSSTANDARDTRIGGERLOADER_H